The invention relates generally to enclosed, cargo transporting trailers and more specifically to such a trailer having at least two sliding side panels which function as doors to permit access to the trailer from the side.
A conventional cargo trailer, the workhorse of the transportation industry, can be accurately and simply described as an elongate, wheeled container having a width of approximately 8 feet, an interior height of between 8 and 10 feet and a length between 30 and 50 feet. The top, sidewalls and bottom of the trailer will typically be rigid panels and access to the interior is generally provided by a pair of hinged, rear doors. While this straightforward design has well served the needs of the transportation industry and those dependent thereon, certain disadvantages are inherent in this design.
First of all, it is readily apparent that cargo disposed in an elongate trailer wherein interior access is available only through one end must be loaded and unloaded sequentially. Two consequences devolve from this difficulty. Since the cargo must be loaded in a sequential fashion, the load/unload time clearly is greater than that which would be experienced if access to a greater portion of the trailer could be obtained at one time, thereby facilitating unloading of greater portions of cargo at one time or through simultaneous utilization of plural unloading agencies such as plural lift trucks. Furthermore, if the cargo consists of disparate articles, it may be necessary to take care to load the trailer in the inverse order in which such disparate cargo will be utilized. If this is not done, it may be necessary to unload substantially the entire cargo before certain first-needed cargo can be retrieved from the trailer. Such a situation has obvious time loss consequences which generally can be overcome only by involving the shipping entity with the material handling requirements of the receiver. Such involvement places a premium on communication and an undue burden on the shipper.
A second difficulty of end loading trailers also relates to the loading/unloading procedure, creates delays and increases the overall time spent in this activity. This difficulty relates to the handling and return of empty parts baskets, empty pallets or other empty cargo carrying devices. Since none of the empty cargo carriers can be returned to the trailer at the cargo utilization site until all of the filled cargo carriers have been removed, numerous additional movements of transport vehicles such as forklifts and additional engagements/disengagements of the carriers by such forklifts are necessitated. For example, a bin or basket may be removed from a trailer, transported to a utilization site in a manufacturing facility where a similar empty bin or basket may be engaged and returned to the loading dock. Until the trailer has been fully emptied, however, the carrier cannot be placed within the trailer. This problem can be brought into sharp relief by envisioning a trailer design and system whereby cargo carriers can be removed from the trailer and transported to their utilization site while empty carriers are returned to the trailer and placed in the space just vacated.
Recent, significant shifts in production methods, inventory techniques and management theories are directed toward the reduction of manufacturing site inventory, compensated for by rapid and timely delivery of components by vendors heretofore warehoused by the user. Such manufacturing and inventory control schemes emphasize, and in fact require, rapid movement of material transported on commercial trailers which is assisted by timely loading and unloading. Side loading trailers further facilitate handling of material of great length such as lumber, pipe and similar elongate goods.
Side loading trailers are known in the prior art. For example, U.S. Pat. No. 4,302,044 discloses a trailer body having slidably openable side panels as well as hinged top panels to provide access to the interior of the trailer in addition to that provided by conventional hinged rear doors. U.S. Pat. No. 3,815,518 discloses a railroad freight car having three side doors in which the middle door may be swung away from the vertical plane of the end doors to facilitate side loading of the car. A review of the foregoing patents and other prior art reveals certain difficulties in designs relating to, for example, the complexity and operational difficulty thereof. It is thus apparent that improvements in the designs of side loading trailers are both possible and desirable.